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Energy HarvestingEnergy HarvestingDevicesDevices

WenWen--JongJong WuWuDepartment of Engineering Science and Ocean EngineeringDepartment of Engineering Science and Ocean Engineering

National Taiwan UniversityNational Taiwan UniversityTel: +886Tel: +886--22--3366576433665764

EE--mail : mail : wjwu@ntu.edu.twwjwu@ntu.edu.tw

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MEMS GeneratorMEMS Generator

Si

Fixed End

Proof Mass

Si

DigitateElectrode

Supporting Membrane

PZT

Proof Mass

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MEMS Generator Impedance CharacteristicsMEMS Generator Impedance Characteristics

• Annealing: 650°C / 120 minutes • Poling:

poled under 200V @ 150 °C60 minutes

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NSCNSC--CNRS International Joint ProjectCNRS International Joint Project

• French side (CNRS) - PI: François COSTA, SATIE Lab Title: Micro-générateurs pour bio-micro-systèmes, basés sur la récupération de l’énergie acoustique grâce à des couches de PZT déposées sur des membranes ou des poutres en silicium.

• Taiwan side(NSC)-PI: Wen-Jong Wu,Co-PI: P.Z. ChangTitle: Micro Generator of Power Harvesting by Vibrations using Innovative PZT Deposition Process

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Using PZT powder in diameter small than 0.5 μm.

Pressure difference between the destination room and powder room：150mmHg ~ 400mmHg

The deposition rate is 0.1 μm/min on a 50x70 mm2 area.

Could be deposited on Si, SiO2, SU-8, glass, polyimide, ITO, Cu, Pt, Au, and Al , etc.

The process is conducted in room temperature.

Annealed in 550~650°C furnance after the jet sprayed process.

Aerosol Jet Sprayed PZT Deposition Chamber Aerosol Jet Sprayed PZT Deposition Chamber

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Material PropertyMaterial PropertyXRD PE curve

Dielectric constant Dielectric loss

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A 15um*800um*650um PZT Released StructureSi

KMPR

PZT(a)KOH backside wet etch

(b)Deposit bottom electrode

(c)Pattern PZT thick film by lift-off.

(d)Deposit Top electrode

(e)Suspend the transformer structure and annealing

PZT

AIR

(residual glue)A freestanding PZT membrane without supporting.

The minimum linewidth of 10 μm thickness PZT structure is 30 μm in our work.

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230

250

270

290

310

330

350

370

2500000 2700000 2900000 3100000 3300000 3500000 3700000 3900000

Frequency (Hz)

Impe

denc

e (O

hm)^

-1

-79.00

-78.00

-77.00

-76.00

-75.00

-74.00

Deg

ree

( o

)

Impedence

Phase

2.80 MHz

3.50 MHz 3.72 MHz

3.82 MHz

3.79 MHz

ANSYS Simulation Mode ShapesANSYS Simulation Mode Shapes

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MMicro Piezoelectric Devices Design and Fabrication Flowicro Piezoelectric Devices Design and Fabrication FlowMicro Piezo Devices

Testing

Device Design

Post Process Design

Annealing Test

Fabrication

The cantilever structure verify that the material properties of jet spray deposited PZT is closed bulk PZT material, and thus the behavior can be precisely simulated and predicted by ANSYS.

The design and fabrication flow of micro piezoelectric devices are as the right figure.

Application for now: Micro power harvesting device and micro piezoelectric transformer, and many other devices can be tried in the future

TransformerCantilever

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Energy Harvesting from Ambient Random VibrationsEnergy Harvesting from Ambient Random Vibrations

• It is an utmost goal to power wireless sensor nodes from energy scavenged from the ambient environment.

• The energy harvesting from ambient vibration with piezoelectric cantilever beam structure has been proven to be one of the best approach toscavenge energy from ambient vibrations due to the high energy density nature of piezoelectric materials.

• The state of the art vibration energy harvesting devices can generate power in milliwatts level.

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Theoretical AnalysisTheoretical Analysis• The mechanical and electrical behavior around the 1st resonant

frequency in bending direction which power harvesting devices usually adopted can be expressed in equivalent circuit model.

– The transformer in the circuit model denotes a mechanical to electrical energy transformation.

– The voltage source E1 denotes a external force– The RmLmCm in mechanical branch denotes equivalent circuit parameters in the

mechanical oscillation. – The C0 in the electrical side denotes the static capacitance of parallel electrode plates

which is shunted with the external electrical load.

FixedFree

E1C0

Lm CmRm

LOAD

Mechanical Branch Figure 1: Beading at 1st Mode

Figure 2: Equivalent circuit Modal

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Experiment architectureExperiment architecture• CC1010

– RF transceiver/ 8051 compatible microcontroller– 2 UART (Universal Asynchronous Receiver / Transmitter) – 3 channel 10Bit ADC– Programmable transmission power

-20dBm to 10dBm for different transmission range

14.7MHz crystal

32KHz crystal

Antenna

Connectors reserved for sensor

Chipcon CC1010

Tunable capacitor

Power connector

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Experimental SetupExperimental Setup

• The experimental setup is composed of a piezoelectric cantilever beam clamped at one end fixed on a vibrating shaker.

• The piezoelectric cantilever beam used here is bimorph type.– The upper panel was used in the frequency tuning purpose.– The lower piezoelectric panel on the beam is then used to harvest energy.

Function Generator

Power Amplifier Vibration Shaker

Bimorph Piezoelectric

Fixed Support End

Microprocessor of the Sensor Netwoks

Harvesting Energy Device

Cantilever Beam

Choosing Different Load

Power Harvesting Device Experimental Setup

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Results of Network Analysis Results of Network Analysis • The two extreme conditions short circuit and open circuit conditions, the

resonant frequencies are 91.5Hz and 94.5Hz respectively. • The 3Hz range is the tunable bandwidth on this system.

– Resonant frequency of the system can be changing in this range by switching in different capacitive loads.

Networks Signal Analysis

30

32

34

36

38

40

42

80 85 90 95 100 105 110 115Frequency(Hz)

Gai

n(dB

)

Shor t C ircu it

Using Tunab le Frequency System

Oper C ircu it

Networks analysis result

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Results of Random Frequency ExcitationResults of Random Frequency Excitation• The device excited under random frequency from 80Hz to 115Hz.

– The average harvesting output power is about 1.53mW with the tuning resonant frequency system turned off and 1.95mW with the resonant frequency tuning system turned on.

– The average harvesting output power increases about 27.4% with the real-time resonant frequency tuning system under random excitation.

Random frequency from 80Hz to 115Hz

0

0.5

1

1.5

2

2.5

3

3.5

4

0 1000 2000 3000 4000 5000 6000 7000

Time(s)

Vol

tage

(V)

No tunable frequency system

With tunable frequency system

Random frequency excitation from 80Hz to 115Hz

1.53mW1.95mW

27.4%+

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Piezo-Transformer

DrivingCircuit

Different typesPiezoelectric Transformer

Self-FilteringModal Electrode

PFC Output 400V

Control Circuit

Constant Current Control

Rigid Support

Innovative P.T.Innovative P.T.--based Inverterbased Inverter

Effieciency:90% !!Phase Control

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• Square wave input Sine wave output

• Modal self-filtering effect

Using P. T. PZTUsing P. T. PZT--MM--5353--2 to light 680mm CCFL2 to light 680mm CCFLInput voltage Output voltage Output voltage Input voltage

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Thank You!!Thank You!!